Spectra Library

The simplest atom — one proton, one electron. Its visible emission lines (the Balmer series) are the historical Rosetta stone of quantum mechanics.

Discovered first in the Sun's spectrum (1868) before being found on Earth. Inert noble gas.

Famous for the bright yellow doublet (Na D lines) responsible for the color of sodium-vapor street lamps.

The reddish-orange glow of classic neon signs comes from a dense forest of lines across the visible spectrum.

Mercury-vapor lamps emit a sharp set of lines used for wavelength calibration in spectroscopy.

Bent triatomic molecule with intense O-H stretching and bending modes; the dominant absorber in atmospheric IR.

Linear triatomic; greenhouse-active because of its strong asymmetric stretch and bending modes in the thermal IR.

Tetrahedral hydrocarbon, simplest alkane. Dominates the IR spectra of gas giants.

Simple primary alcohol; broad O-H stretch is its IR signature, and its ¹H NMR shows three distinct environments.

Archetypal aromatic ring. Strong UV π→π* bands and a characteristic ring-breathing Raman mode at 992 cm⁻¹.

Simplest ketone; the very strong C=O stretch near 1715 cm⁻¹ is a textbook IR marker.

Purine alkaloid responsible for the world's most-consumed stimulant. Strong UV absorption is used for quantification.

Acetylsalicylic acid; contains both ester and carboxylic-acid carbonyls, giving a distinctive IR.

Most abundant monosaccharide. Multiple O-H stretches and a rich fingerprint region from C-O-C and C-O-H modes.

Iron's atomic spectrum is famously dense — thousands of lines make it a workhorse for stellar metallicity measurements.

Reddish flame test (670.8 nm). Used in metallurgy and batteries.

Violet flame; doublet near 766/770 nm dominates K-discharge.

Ca II H & K lines are the deepest features in the solar UV.

Mg b triplet near 518 nm is a classic visible feature.

Pink-violet discharge. Used in Ar lasers and lamps.

Used to define the metre (1960–1983) via the 605.78 nm line.

White-blue flashtube spectrum approximating sunlight.

Atomic O lines responsible for green/red airglow.

N₂⁺ first-negative bands give the aurora's blue/violet bottom.

C I and C₂ Swan bands feature in comet and flame spectra.

Blue-green flame test; intense doublet in atomic absorption.

Bluish discharge; lines used in atomic absorption.

Sharp UV resonance doublet; visible lines are weaker.

Au resonance line at 242.8 nm; visible discharge is weak.

Crimson flame, red fireworks. Sr I/II lines in visible.

Doublet near 780/795 nm; basis of Rb atomic clocks.

D-lines used to define the second (since 1967, hyperfine).

Mn I triplet near 403 nm is prominent in stellar UV.

Dense visible spectrum from d-electron transitions.

Pb 405.8 nm widely used for trace lead determination.

Sharp UV doublet near 309 nm; faint visible lines.

Si I lines in the near-UV, plus 288.2 nm AAS line.

S I lines lie mostly in UV and IR; flame color is blue.

Greenish discharge; many lines in red and near-IR.

Reddish-orange vapor; many lines in green and red.

I₂ molecular bands dominate visible (yellow→violet).

Ti II lines and TiO bands dominate cool-star spectra.

Cr triplet near 425 nm; intense in steel discharges.

Pyramidal C₃ᵥ molecule; classic umbrella-inversion tunneling at 23.8 GHz.

Diatomic; the rotational ladder at 2.6 mm is the workhorse of molecular astronomy.

Homonuclear diatomic — IR inactive; Raman active.

Triplet ground state; Raman line at 1556 cm⁻¹.

Bent C₂ᵥ; Hartley UV band (200–310 nm) shields the biosphere.

Bent like H₂O but with much weaker hydrogen bonding.

Diatomic with strong P/R branches from Cl isotopologues.

Strongest H-X stretch; H-bonded chains in condensed phase.

Open-shell radical; biological signaling molecule.

Brown gas; bent C₂ᵥ; visible absorption gives smog its color.

Bent C₂ᵥ; UV bands used in volcano monitoring.

Simplest C-C bond. Found in Titan's lakes.

Common LPG fuel.

Common nonpolar solvent.

Simplest alcohol; broad O-H stretch and sharp C-O.

Doublet methyl + septet methine.

Carboxylic acid: very broad O-H + C=O near 1710.

Ester C=O ~1740 + strong C-O at 1240/1050.

Methylbenzene; UV bands shifted from benzene; NMR ring + methyl.

Aromatic O-H 3200–3500 + ring modes.

Two N-H stretches + ring modes.

Strong asym/sym NO₂ pair at 1520/1345.

Aldehyde C=O 1745 + characteristic 2820/2720 doublet.

Aldehyde with diagnostic methyl + CHO quartet.

Simplest carboxylic acid.

Two N-H regions + C=O.

Zwitterionic in solid; NH₃⁺/COO⁻ stretches.

Methyl doublet + quartet alpha-H.

β-pyranose form; ring CH proton at 4.65 ppm vs α 5.23.

Glucose-fructose disaccharide; O-H rich IR.

Purine base; strong UV near 260 nm.

Pyrimidine; λmax 267 nm.

Purine with C=O; λmax 246 + shoulder.

Pyrimidine with methyl; λmax 264 nm.

RNA base; λmax 259 nm.

Magnesium porphyrin; Soret band ~430 + Q-band ~660 nm.

Conjugated polyene; three vibronic peaks 425/450/478 nm.

Iron porphyrin; Soret near 410 nm.

Push-pull chromophore; broad 600 nm absorption gives jeans blue.

Thiazine dye; intense λmax 664 nm.

Flavin chromophore; yellow color from 445 nm.

Enediol lactone; λmax 265 nm.

Ketose isomer of glucose.

Amide N-H + aromatic O-H + C=O.

Carboxylic acid + isobutyl + aromatic.

Sharp C≡N stretch at 2253 cm⁻¹.

Strong S=O stretch 1050 cm⁻¹.

Amide C=O ~1670 + restricted rotation gives two NMR methyls.

C-Cl stretches in 700–800 region.

Singlet at 7.26 in NMR — standard CDCl₃ residual.

Tₐ — IR inactive symmetric stretch but Raman active.

IR calibration standard; many sharp peaks 700–3100.

Polyamide: amide I + II classic.

Ester C=O 1715 + aromatic C-O 1250.

Broad O-H + dense C-O fingerprint.

Intramolecular H-bond → red-shifted UV.

Fused aromatic; multiple π→π* bands.

Vibronic UV-vis structure 320–380 nm; fluorescent.

Ring with N — distinctive Raman 991 cm⁻¹.

Tryptophan fluorophore; N-H at 8 ppm.

Indole chromophore drives 280 nm protein absorbance.

Phenol chromophore at 274 nm.

Pure sp³ alkane; clean CH₂ stretches.

C=C stretch 1623 cm⁻¹ — IR forbidden but Raman active.

C≡C 1974 (Raman) + ≡C-H 3289 (IR).

Two N-H stretches + N-H bend.